This invention relates generally to impact printers and more particularly to improvements in type means for printing large solid blocks.
Impact printers of various designs are very well known in the art and are used extensively as output devices in computer systems. One type of impact printer employs a plurality of aligned individually actuatable hammers mounted opposite to a moving type surface such as a rotating drum or linearly moving belt. The type surface has raised characters formed thereon which move past the faces of the hammers. In the case of a drum, the characters normally move perpendicular to the line of hammers. In the case of a belt, the characters normally move along the line of hammers.
An ink ribbon and the paper to be printed upon pass between the hammers and type surface such that actuation of a hammer causes it to impact against the type surface, thus printing the impacted character on the front side of the paper adjacent the ribbon. After a full line is printed, the paper is stepped for printing a subsequent line.
Regardless of the kind of type surface employed, it will typically carry a full set of alphanumeric characters for movement past each hammer face. Since each hammer normally impacts against all characters with the same force, the density of the printed character will vary inverse to the land area or contact area presented to the hammer face. That is, very large land area characters will print light and very low land area characters will print dark.
Applications have recently arisen which require the printing of vastly different size characters on a document. For example, labels for use on supermarket shelves normally identify the product in standard size type and display the price in very large type. If an impact printer is to be used to print such labels and if the large type is to consist of characters larger than the area of a hammer face, then it is necessary to form the large characters modularly, i.e., by printing standard size characters positioned relative to one another to form the large type characters. Attempts have been made to form such large type characters utilizing standard size characters in the shape of solid blocks of rectangular and triangular configuration. One of the significant problems, however, encountered with this approach is that the high land area constituted by such a solid block results in low density (light, grey) printing. This, of course, may be unacceptable in many applications; particularly where the label is being used for display purposes, as in the aforementioned supermarket application.